docs: def set_source_filter(self, source):
          """ Only search for tweets entered via given source
  
          :param source: String. Name of the source to search for. An example \
          would be ``source=twitterfeed`` for tweets submitted via TwitterFeed
          :raises: TwitterSearchException
          """
  
          if isinstance(source, str if py3k else basestring) and len(source) >= 2:
              self.source_filter = source
          else:
              raise TwitterSearchException(1009)